A new DYN3D library for the WWER-1000 reactors

A new library of two-group diffusion and kinetics parameters has been generated for the neutron kinetics code DYN3D, intended for analysis of reactivity initiated accidents for the WWER-1000 reactors. All assembly types for the 3-year fuel cycle are included. The Helios-1.5 code and its adapted 190-group library have been used at the stage of the lattice calculations. A generalised code for preparation of Helios input for both types of WWER reactors has been developed. The approximation methodology is based on a combination between interpolation over the moderator temperature and density, and approximation over the rest of the independent state parameters. High accuracy is achieved by applying square interpolation over the moderator temperature and cubical interpolation over the moderator density. The axial/radial reflectors are described by effective diffusion parameters, including reference discontinuity factors, calculated on the base of one/two-dimensional heterogeneous 23-group transport theory solutions by Mariko. DYN3D has been modified in order to use the new library. BIPR-7 results, used for operational neutronics calculations of the WWER-1000 reactors at the Kozloduy NPP, have been used to validate the new library. The kinetics parameters have been validated as well.